Let-off mechanism



Mar. '13, 1923.

OFF MECHANISM J. NORTHROP Filed May 15, 1920 In- 4 H. g

LET

MM Z W M Z w Patente Mar. 13, 1923,

a? win-ES 1 rear JONZQS NORTHROP, OF HOPEDALE, MASSACHUSETTS, ASSIGNQR TO HGPEDALE MANU;

FACTUBING COMPANY, OF MILFORD, MASSACHUSETTS, A CORPORATION OF MASSA- CHUSETTS.

Application filed May 13,

To all whom it may concern:

Be it known that I, JoNAs NORTHROP, a citizen of the United States, residing at, Hopedale, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Let- Ofi' Mechanism; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will en-- able others skilled in the art to which it appertains to makeand use the same.

The present invention relates to a let off mechanism for looms.

The object of the invention is to produce a let off mechanism of novel and efiicient construction adapted to let off the warp threads from the warp beam in such a manner as to maintain a uniform tension thereon. To this end a feature of the invention contemplates a construction of let off mechanism in which the rate of let off of the warp is controlled by the tension on ,the warp threads to the'end that a uniform tension is maintained at all times. The invention con- 25. sists in the mechanism hereinafter described and particularly pointed out in the claims.

-1 In the drawings illustrating the preferred embodiment of the invention, Figure 1 is a side elevation of a portion of a loom showin g the improved let off mechanism; Fig. 2 is a vertical section taken on the line 22 Fig;

1 and Fig. 3 is a section taken on the line- 3-3, Fig. 2. I

The let off mechanismillustrated in the drawings comprises in general. a warp beam, a movable whip roll over which the warp threads pass as they unwind from the warp beam means for rotating the warp beam, and a mechanism cooperating with the whip the rate of let off of the warp in accordance with variation in the tension ofthe warp threads in order to maintain the tension uni-form.

Referring to the drawings, thewarp threads 10 are unwound from the warp beam 12 mounted on the shaft 13, journaled in the loom frame 14, pass over a whip roll 15 and thence through 'the harness to the wind up roll at the frontof the loom in a manner well known and familiar to those skilled in the art.

The warp threads 10 are left off from the warp beam 12 by mechanism which is deroll and with said means adapted to control LET-Orr MECHANISM.

1920. Serial No. 881,017.

scribed as follows: A let off pawl 20 is pivotallyl mounted upon the stud 21 upon one end of a pawl lever 22 pivoted on a vertical shaft 23. The vertical shaft 23 is supported in bearings 24 in a supporting member 25, secured to the loom frame. The let off pawl 20 is adapted to cooperate with a ratchet wheel 26, also mounted upon the shaft 23, and secured thereto by a set screw 27. The let off pawl 20 is adapted to be oscillated back and forth with the lever 22 about the vertical shaft 23 as a pivot upon each beat of the lay, the lever 22 being connected to the sword 28 of the lay by a link 29. The rotations of thevertical shaft 23 are transmitted to the warp beam 12 through a worm 34 and a worm wheel 35' on the counter shaft 36, journaled in a supporting bracket 37 secured to the loom frame by means of a pinion 38 which meshes with the gear 39 on the warp beam. A friction brake 40, comprising a drum 41 secured upon the shaft 23 and the brake strap 42 yieldingly held in contact with the drum by a spring 43, operates to hold the shaft 23 from unintentional movement and to permit actuation of the shaft whenever the ratchet wheel 26 is advanced in the operation of letting off the warp. In this manner the shaft 23 may.

be advancedv and will stay in any position 4 to which it is moved. The link 29 is provided at its rear end with a slot 50 which receives the pin 51 in the end of the lever 22 opposite to the pawl end of the lever. As the sword swings back and forth, the slot 50 in the link 29- engages the pin 51 and moves the lever 22 in a direction to advance the ratchet wheel. A spring 52 on the hub of the pawl lever 22 normally tends to rostand and rotated to adjust it in and out.

through the boss on the head 53, so as thereby to change the position ofthe path of movement of the slot 50. A coil spring 54 normally received in a socket in the lever 22 presses upon the tail of the pawl lever 20 so as to hold the pawl in engagement with the action of the pawl lever spring 52.

When the pawl holder is moved back to the position illustrated in Fig. 3, the link 29 will be prevented from engaging or moving the pawl until the end of the slot comes in contact with thepin 51, and under such circumstances the pawl lever will have a certain limited amplitude of oscillation. if

the pawl holder is moved back farther, obviously the link 29 will pick it up earlier and the are of oscillation of the pawl lever will be increased.

The pawl holder 56 is controlled and operated by the tension on the warp above and below the normal operating value. To this end the whip roll 15 is provided with hearing boxes 68 slidably mounted in the slots 69 in arms 70 extended rearwardly from a shaft 71 rotatably supported in U-shaped bearings 72 of a bracket 73, and bolted to the loom frame. The whip roll 15 is yieldingly held rearwardly by light springs 74 which cooperate with the bearing boxes 68 and permit a slight yield as the shed opens and closes. The arms 70 are secured to the shaft 71 to move therewith by set screws, one of which is shown at 7 5. A depending whip roll lever arm 85 comprising three members 86, 87 and 88, is mounted upon the outer end of the shaft 71 and is secured in fixed relation to the shaft 71 by any suitable means, such as the cap nut 89. The lower member 88 of the lever arm 85 carries the pawl holder 56 which is extended at right angles thereto and adapted to loosely engage the pawl arm 55 which extends downwardly as has been described. from the lower side of the pawl lever 22. The lower member 88 and the upper member 86 are bolted to an intermediate member 87 to form the complete lever arm 85. A vertically arranged slot 90 in the lower member 88 permits the vertical adjustment thereof, and a horizontal slot 91 in the intermediate member 87 permits angular adjustment of the members 87 and 86. ft will therefore be observed that whenever the whip roll shaft 71- is oscillated, the lever arm 85 is swung about the axis of the shaft? 1 as a pivot, and operates through the engagement of the pawl holder 56 with the arm 55 to change the amplitude of oscillation of the pawl lever 22. A red 99 is pivotally secured to-the lower end of the upper member .86 of the lever arm 85, having its rear end screwed into a connector 100 pivotally secured to the upper member 86- The front end of the rod 99 is extended through and supported as er by a bracket 101 laterally extended from the loom frame 1 1-. A coil spring 102 embraces the rod 99, its front end abutting the bracket 101 and its rear end abutting a collar 103 screwed upon the rear end of the rod 99 and held in adjusted position by a lock nut 104 so that the tension of the coil spring 102 may be adjusted.

From the foregoing description it will be apparent that the tension upon the warp threads operates through the whip roll 15 to rotate the whip roll shaft 71, as viewed in Fig. 1 in a clockwise direction, and also that the coiled spring 102 operates with the lever arm to resist this tendency of the shaft 71 to rotate. 1f the tension in the coil spring is initially adjusted by means of the position of the lock nut 104 on the rod 99 so that the normal operating tension on the warp threads is exactly compensated for and the lever arm 85 is balanced in its normal position, it will be apparent that any variations which may occur in the tension of the warp threads will operate to cause movement of the lever arm 85 in either one direction or the other, accordingly as the tension is increased or decreased.

In the normal operation of the loom the cloth is wound up on the wind-up roll at the front of the loom. As the cloth is wound up in this manner the tension of the warp gradually increases. As soon as the tension increases sufficiently to depress the whip roll 15, the lever 85 is moved in a direction to withdraw the pawl holder 56 so as to permit the pawl lever to swing back farther under the influence of its spring. This re sults in increased amplitude of oscillation of the pawl lever and increased movement of the ratchet wheel, and actuates the warp beam through the means described to let off the warp and thereby restore the tension to the normal amount. The letting off of the warp continues until the tension on the warp decreases suficiently to allow the spring 102 to move the depending whip roll lever arm 85 in a direction to reduce or entirely stop the oscillations of the pawl lever. Thereupon the warp beam stands fast until the tension of the warp increases sufliciently again to cause the operation of the actuating mechanism for the warp beam. In ordinary operation of a loom the oscillations of the pawl lever will be permitted by the pawl holder to be such as to let off the precise amount of warp threads to keep the maximum rate corresponding with the minimum usable diameter of the warp upon the warp beam.

The improved let off mechanism is extremely sensitive in operation, and serves to control the rate of let off in strict accordance with the variations in tension on the warp at all times and under all operating conditions.

While the preferred embodiment of the invention-has been illustrated and described, it will be understood that the same may be embodied in other forms within the scope of the following claims 1. A let off mechanism for looms having, in combination, a. warp beam, a 'ratchet wheel, and connections between the ratchet wheel and warp beam for actuating the warp beam to let off the warp, means for actuating the ratchet wheel, comprising a pawl lever, a pawl carried byv the pawl lever, said pawl lever being provided with a depending pawl arm, a whip roll, a whip roll lever arm provided with a pawl holder laterally extended from the arm for engaging the pawl arm and limiting the pawl movement to lesser and greater distances determined by the tension of the warp.

2. A let off mechanism for looms having, in combination, a warp beam, a ratchet wheel, a shaft upon which the ratchet wheel is mounted, gearing connections between the shaft and the Warp beam, said shaft being arranged inv vertical position, a pawl lever located adjacent to the ratchet wheel pr0-,v

vided with a pin, a slot-ended link engaging the pin on the pawl lever, a spring moving the-pawl lever in one direction, a whip roll, an arm connected with the whip roll carrying a pawl holder acting to limit the retracting movements of the pawl lever due to the action of the spring thereon.

JONAS NORTHROP. 

